Windows generally share a common function, whether glass or plastic and whether used in buildings, automobiles, aircraft, boats, motorcycle visors, or glasses: to permit light transmission into a physical structure. Users of vehicles such as automobiles, aircraft, boats, and planes, have especially benefited from the use of windows, as they provide protection from the elements while still permitting visual acuity.
Most conventional windows have only a single transmissivity state. Thus, whether it be rain or shine, dusk or dawn, or noon or night, most conventional windows transmit virtually all available light. Although this may be desirable in many circumstances, such as during periods of low light levels, in other circumstances it may be less than optimal. For example, as any vehicle operator has experienced, under some circumstances (e.g., a due east heading on a clear and crisp morning), this limitation of conventional windows becomes quite noticeable. When the vehicle is an aircraft, the pilot and other personnel located in the cockpit of the aircraft under such circumstance may experience discomfort and non-optimal visual capability.
Light to a pilot's eyes may come directly (from the sun) and indirectly (reflected from other surfaces), and may cause several problems for the pilot. Too much or too little light may undesirably reduce the visual acuity of the pilot. Rapid changes in light intensity may require rapid pupil diameter changes, and may cause the pilot to experience temporary visual acuity loss. Situations such as laser attacks or light reflections from other surfaces may combine more than one problem for a pilot, either too much light or too rapid a change in light intensity, or both.
Furthermore, radiation from across the electromagnetic spectrum may be released from the sun and absorbed by a pilot's skin in the form of heat. When a pilot absorbs too much heat, the pilot may experience discomfort and may have a reduced level of performance. “Gaspers” or vents are used by pilots to reduce body temperature. While these devices have some effectiveness, they function by convective cooling, which removes water vapor from skin and may cause skin to seem dry and cause discomfort. Additionally, multiple pilots in a cockpit may absorb different amounts of heat from the sun (for instance, if one is in direct sunlight and one is in shade) and therefore require different levels of cooling to remain comfortable, which is hard to achieve with vents.
Systems and methods for providing aircraft cockpit windows and the like with variable light transmission capability would therefore have utility.